Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Patent
1990-05-17
1993-01-26
Weinhardt, Robert A.
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
G11B 700
Patent
active
051827379
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a system for reading an optical recording medium having a data region formed by arranging, in parallel, a plurality of data tracks each of which is constituted by a plurality of bits along reference lines which are perpendicular to the data tracks.
BACKGROUND ART
In an optical recording medium having a data region formed by arranging, in parallel, a plurality of data tracks each of which is constituted by a plurality of bits along reference lines which are perpendicular to the data tracks, two reference lines are provided and their interval is arranged to be larger than the interval between other data bits so that the reference lines can be easily distinguished from the data bits in a read signal.
A data reading apparatus for reading data from the optical recording medium of the type described above performs the reading operation and identifies the data bits with reference to the positions of the above-described reference lines.
However, the above-described conventional optical recording medium suffers from a poor recording capacity since it has the above-described two reference lines having a large interval in each of the data regions thereof.
If the interval between the reference lines is reduced or the number of the reference line is decreased by one for the purpose of enlarging the recording capacity, the identification of the reference line becomes unstable, causing a problem in terms of the reliability of the reading apparatus.
DISCLOSURE OF THE INVENTION
Accordingly, it is an object of the present invention to provide a reading system with which the capacity of the optical recording medium can be enlarged.
In order to achieve the above-described object, according to the present invention, there is provided a system for reading an optical recording medium having a data region formed by arranging, in parallel, a plurality of data tracks each of which is constituted by a plurality of bits along a reference line positioned perpendicular to the data tracks, the system for reading an optical recording medium being characterized by a reading portion having: a bit included in the data track and positioned adjacently to the reference line and arranged to be a clock bit; a counter for generating a clock window on the basis of a read signal of the data track; an AND circuit for calculating the logical product of the clock window and the read signal of the clock bit in the present data region and generating a true clock pulse or a dummy clock pulse; a counter for converting the dummy clock pulse into the timing of the true clock pulse in the case of the dummy clock pulse; a counter for generating a data window on the basis of the true clock pulse; and an AND circuit for calculating the logical product of the data window and the read signal so as to make the logical product to be the data.
As a result of the above-described structure, even if the number of the reference lines in the optical recording medium is decreased to one, data can be correctly read so that the data recording capacity can be significantly enlarged.
According to other aspects of the present invention, the interval between the clock bit and the reference line is arranged to be different from intervals between other bits and the clock bits are formed on alternate data tracks, or a counter for generating an upper window for displaying the difference between the present data region and the neighboring data region is included therein.
Furthermore, the clock windows are generated at the same intervals between the reference lines and the clock bits, or the data windows are generated at the same intervals between the data bits.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a block diagram which illustrates an embodiment of a reading system according to the present invention:
FIG. 2 is a time chart which illustrates the operation of reading an optical recording medium performed on the basis of the reading system;
FIG. 3 is an enlarged view which illustrates an essential portion of the o
REFERENCES:
patent: 4855981 (1989-08-01), Kimura et al.
Hindi Nabil
Kabushiki Kaisha CSK
Weinhardt Robert A.
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